Turnover of plant lineages shapes herbivore phylogenetic beta diversity along ecological gradients

Understanding drivers of biodiversity patterns is of prime importance in this era of severe environmental crisis. More diverse plant communities have been postulated to represent a larger functional trait‐space, more likely to sustain a diverse assembly of herbivore species. Here, we expand this hypothesis to integrate environmental, functional and phylogenetic variation of plant communities as factors explaining the diversity of lepidopteran assemblages along elevation gradients in the Swiss Western Alps. According to expectations, we found that the association between butterflies and their host plants is highly phylogenetically structured. Multiple regression analyses showed the combined effect of climate, functional traits and phylogenetic diversity in structuring butterfly communities. Furthermore, we provide the first evidence that plant phylogenetic beta diversity is the major driver explaining butterfly phylogenetic beta diversity. Along ecological gradients, the bottom up control of herbivore diversity is thus driven by phylogenetically structured turnover of plant traits as well as environmental variables.     

Structure of the tetragonal surface virulence array protein and gene of Aeromonas salmonicida

The paracrystalline surface protein array of the pathogenic bacterium Aeromonas salmonicida is a primary virulence factor with novel binding capabilities. The species-specific structural gene (vapA) for this array protein (A-protein) was cloned into lambda gt11 but was unstable when expressed in Escherichia coli, undergoing an 816-base pair deletion due to a 21-base pair direct repeat within the gene. However, the gene was stable in cosmid pLA2917 as long as expression was poor. A-protein was located in the cytoplasmic, inner membrane and periplasmic fractions in E. coli. The DNA sequence revealed a 1,506-base pair open reading frame encoding a protein consisting of a 21-amino acid signal peptide, and a 481-residue 50,778 molecular weight protein containing considerable secondary structure. When assembled into a paracrystalline protein array on Aeromonas the cell surface A-protein was totally refractile to cleavage by trypsin, but became trypsin sensitive when disassembled. Trypsin cleavage of the isolated protein provided evidence that both the NH2- and COOH-terminal regions form distinct structural domains, consistent with three-dimensional ultrastructural evidence. The NH2-terminal 274-residue domain remained refractile to trypsin activity. This segment connects by a trypsin and CNBr-sensitive 78-residue linker region to a COOH-terminal 129-residue fragment which could apparently refold into a partially trypsin-resistant structure after cleavage at residue 323.     

Suppressor T cell growth and differentiation: production of suppressor T cell differentiation factor by the murine thymoma BW5147

Previous studies have identified a lymphokine, termed Ts differentiation factor (TsDF), in primary MLR supernatants that induces effector function of alloantigen-primed MLR-Ts. The present report describes constitutive production of TsDF by the murine thymoma BW5147, and its use to analyze alloantigen and TsDF requirements for MLR-Ts activation to TsF production. Serum-free supernatants of BW5147 restored the capacity of MLR-TsF production to alloantigen-primed MLR-Ts cultured with glutaraldehyde-fixed allogeneic stimulator cells, and were not themselves directly suppressive in the MLR assay. BW5147 supernatant induced MLR-TsF production from primed L3T4-Ly2+ MLR-Ts in the absence of concomitant proliferation, suggesting that the function of BW5147 supernatant, like that of MLR-derived TsDF, is a differentiative rather than a proliferative one, and is required for the synthesis or release of TsF. The differentiative activity of BW5147 supernatant was associated with a molecular species of approximately 14,500 m.w. by HPLC fractionation and was expressed independently of detectable IL 2, IL 3, IFN-gamma, and IL 1. The functional activity of BW5147 supernatant has therefore been provisionally designated BW5147-derived Ts differentiative factor, or BW-TsDF. By using BW-TsDF, it was demonstrated that MLR-Ts fail to respond to TsDF in the absence of, or preceding, reexposure to priming alloantigen. Instead, alloantigen binding by primed MLR-Ts appears to create a transient state of TsDF responsiveness. Primed MLR-Ts were fully sensitive to delayed addition of TsDF for approximately 12 hr after reexposure to alloantigen, but became TsDF-unresponsive within 24 to 36 hr. MLR-Ts cultured alone for 36 hr were fully responsive to the combined addition of TsDF and alloantigen. Thus, MLR-Ts activation to TsF release requires the sequential events of specific alloantigen binding, which induces a TsDF-responsive state, followed by interaction with TsDF. The transience of induced TsDF responsiveness suggests a precise mechanism for control of antigen-initiated Ts activation to effector function.     

CORRESPONDENCE BETWEEN PHYLOGENY AND MORPHOLOGY OF SNOWELLA SPP. AND WORONICHINIA NAEGELIANA,CYANOBACTERIA COMMONLY OCCURRING IN LAKES1

In this study, the first reported isolates of the genera Snowella and Woronichinia were characterized by 16S rRNA gene sequencing and morphological analysis. Phylogenetic studies and sequences for these genera were not available previously. By botanical criteria, the five isolated strains were identified as Snowella litoralis (Häyrén) Komárek et Hindák Snowella rosea (Snow) Elenkin and Woronichinia naegeliana (Unger) Elenkin. This study underlines the identification of freshly isolated cultures, since the Snowella strains lost the colony structure and were not identifiable after extended laboratory cultivation. In the 16S rRNA gene analysis, the Snowella strains formed a monophyletic cluster, which was most closely related to the Woronichinia strain. Thus, our results show that the morphology of the genera Snowella and Woronichinia was in congruence with their phylogeny, and their phylogeny seems to support the traditional botanical classification of these genera. Furthermore, the genera Snowella and Woronichinia occurred commonly and might occasionally be the most abundant cyanobacterial taxa in mainly oligotrophic and mesotrophic Finnish lakes. Woronichinia occurred frequently and also formed blooms in eutrophic Czech reservoirs.     

Ruddy turnstones Arenaria interpres rapidly build pectoral muscle after raptor scares

To cope with changes in the environment, organisms not only show behavioural but also phenotypic adjustments. This is well established for the digestive tract. Here we present a first case of birds adjusting their flight machinery in response to predation risk. In an indoor experiment, ruddy turnstones Arenaria interpres were subjected to an unpredictable daily appearance of either a raptor or a small gull (as a control). Ruddy turnstones experiencing threat induced by a flying raptor model, longer than after similar passage by the gull model, refrained from feeding after this disturbance. Pectoral muscle mass, but not lean mass, responded in a course of a few days to changes in the perceived threat of predation. Pectoral muscle mass increased after raptor scares. Taking the small increases in body mass into account, pectoral muscle mass was 3.6% higher than aerodynamically predicted for constant flight performance. This demonstrates that perceived risk factors may directly affect organ size.